The present invention relates to an air-conditioning duct that is located inside an automobile interior part such as a console box and an instrument panel.
Conventionally, a vehicle has air-conditioning ducts for conveying air from an air conditioner. Such ducts are often located inside interior parts such as a console box and an instrument panel. When an air-conditioning duct is arranged inside an automobile interior part, dew condensation can occur on the surface (ornamental surface) of the interior part due to the temperature difference between the interior of the air-conditioning duct (air passage) and the exterior (the interior of the passenger compartment). Accordingly, a countermeasure has been taken to prevent formation of dew condensation by forming a backside of an automobile part to be heat-insulated.
For example, in an instrument panel disclosed in Japanese Laid-Open Patent Publication No. 2003-170762, a portion inside a predetermined position located at an opening of an air-conditioning duct is made thicker than the remainder of the instrument panel. A foam portion (a dew condensation suppression portion) is formed in the thick portion. The foam portion is formed in the following manner. First, a forming material containing a blowing agent is injected into a cavity of a mold. Then, the thickness (volume) of the cavity is partly expanded to lower the pressure. This causes the blowing agent to produce foam. The foam portion increases the heat insulating property of the predetermined portion. This suppresses the formation of dew condensation on the surface of the instrument panel.
Japanese Laid-Open Patent Publication No. 2003-326942 discloses a configuration of an instrument panel in which urethane material is sprayed to a portion about an air outlet using a spray gun. Utilizing the adhesion of the urethane material when it is hardened, the duct is coupled to the instrument panel. A urethane layer (dew condensation suppression portion) formed by hardening the urethane material increases the heat insulating property about the air outlet. This suppresses the formation of dew condensation on the surface of the instrument panel.
To efficiently improve the heat insulation property of an automobile interior part, a dew condensation suppression portion is preferably formed evenly in the entire area of a predetermined portion that forms part of an air passage. That is, if an automobile interior part has uneven sections such as salient corners and steps, the dew condensation suppression portion is preferably formed along the uneven portions. However, when adopting such a configuration, since Japanese Laid-Open Patent Publication No. 2003-170762 forms a dew condensation suppression portion by injection molding during the molding of an instrument panel, a mold having a complicated shape needs to be used. This increases the manufacturing costs. On the other hand, in the configuration of Japanese Laid-Open Patent Publication No. 2003-326942, since the urethane material is manually sprayed using a spray gun, it is difficult to evenly spray the material along the uneven portion. Such spraying of urethane material is thus troublesome. In addition, it is highly likely that the sprayed amount of the urethane material varies among the products, which can result in wasted material.
Accordingly, to eliminate the increase of manufacturing costs, waste of material, and the complexity of manufacturing procedures that accompany the forming of such a dew condensation suppression portion (the foam portion in Japanese Laid-Open Patent Publication No. 2003-170762, and the urethane layer in Japanese Laid-Open Patent Publication No. 2003-326942) in an automobile interior part, a method has been proposed in which a dew condensation suppression portion is formed in a position that is as spaced as possible from uneven portions, that is, the space adjacent to the dew condensation suppression portion is maximized. However, in a configuration where the space between a dew condensation suppression portion and an uneven portion is maximized, an area in the predetermined portion that is occupied by the dew condensation suppression portion is reduced. This is likely to reduce the heat insulation property of the interior part. Therefore, in terms of improving the heat insulation property, the space adjacent to the dew condensation suppression portion is preferably minimized.
As described above, in case of an automobile interior part provided with a dew condensation suppression portion, there are two contradicting demands, that is, a demand for forming a space adjacent to the dew condensation suppression portion for eliminating the difficulty of forming the dew condensation suppression portion, and a demand for eliminating such space for improving the heat insulation property.